The participants start on a bank of an imaginary acid river. There are a number of tree stumps sticking above the river’s surface. The group has three planks which they may use to cross the river. If any group member falls off a plank or a stump while crossing the river, or should any of the planks touch or fall into the river, the group must start over again. Great for problem solving, patience, and getting the group to work as one unit.